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Electronics Repair (sci.electronics.repair) Discussion of repairing electronic equipment. Topics include requests for assistance, where to obtain servicing information and parts, techniques for diagnosis and repair, and annecdotes about success, failures and problems. |
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#1
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Sony KV-35S26 - Picture collapses
I have a Sony KV-35S26 that I acquired with a bad power supply and
shorted HOT. It was deader than a doornail. Using information acquired from these posts, I replaced two switching transistors in the power supply (2SC4834), the HOT, and the blown fusible resistor (0.1 ohm R607) on the power supply. Voila! The television works great--except . . . After the set is on for a while, all of sudden the right side of the picture starts to contract and cave in. Then the horizontal deflection gives way to a picture that contracts into the middle and goes black. At this point I've always quickly turned off the set, assuming that if something's not oscillating I'm probably on the verge of shorting out the parts that I just replaced. I let the set sit--sometimes for 30 seconds, sometimes for a couple of minutes--and when I turn it on again I once more have a very nice picture. Then after another few minutes of running, the same thing happens again. It starts to get fuzzy and contract along the right side, and then it collapses. I should also mention that when I replaced the HOT, I also went through the HOT circuit and meticulously resoldered every connection (there were a few that looked like they might have had ring cracks at the solder joint). I also resoldered the flyback transformer. The intermittent nature of the problem after the set's been on a while makes me wonder if it's heat related. In addition to the components mentioned above, are there other common failure points in the horizontal output circuitry? I sincerely appreciate any help you might be able to offer. Best wishes, Juan |
#2
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Sony KV-35S26 - Picture collapses
Most likely you either missed a connection in the h-drive circuit or you
have a badelectrolytic in that circuit. There is a small value electrolytic, .47uF IIRC, that is reported to be a high failure part in the sony h-drive circuits. I have not found many bad ones. The culprit is usually bad solder joints. Check the pin circuit as well. Leonard "Juan" wrote in message ups.com... I have a Sony KV-35S26 that I acquired with a bad power supply and shorted HOT. It was deader than a doornail. Using information acquired from these posts, I replaced two switching transistors in the power supply (2SC4834), the HOT, and the blown fusible resistor (0.1 ohm R607) on the power supply. Voila! The television works great--except . . . After the set is on for a while, all of sudden the right side of the picture starts to contract and cave in. Then the horizontal deflection gives way to a picture that contracts into the middle and goes black. At this point I've always quickly turned off the set, assuming that if something's not oscillating I'm probably on the verge of shorting out the parts that I just replaced. I let the set sit--sometimes for 30 seconds, sometimes for a couple of minutes--and when I turn it on again I once more have a very nice picture. Then after another few minutes of running, the same thing happens again. It starts to get fuzzy and contract along the right side, and then it collapses. I should also mention that when I replaced the HOT, I also went through the HOT circuit and meticulously resoldered every connection (there were a few that looked like they might have had ring cracks at the solder joint). I also resoldered the flyback transformer. The intermittent nature of the problem after the set's been on a while makes me wonder if it's heat related. In addition to the components mentioned above, are there other common failure points in the horizontal output circuitry? I sincerely appreciate any help you might be able to offer. Best wishes, Juan -------------------------------------------------------------------------------- I am using the free version of SPAMfighter for private users. It has removed 18141 spam emails to date. Paying users do not have this message in their emails. Try SPAMfighter for free now! |
#3
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Sony KV-35S26 - Picture collapses
Replace VDR 601, it's black, there may be two depending on the model,
they are by the two 2sc4834 regulators. They go bad sometimes. Be sure to resolder the horizontal drive, & check the electrolytic capacitor, if it has one, Dani. |
#4
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Sony KV-35S26 - Picture collapses
Why would you replace the VDR in this case? The VDRs almost never go bad
when the cause of the failure is the output stage shorting. Leonard "Dani" wrote in message ups.com... Replace VDR 601, it's black, there may be two depending on the model, they are by the two 2sc4834 regulators. They go bad sometimes. Be sure to resolder the horizontal drive, & check the electrolytic capacitor, if it has one, Dani. -------------------------------------------------------------------------------- I am using the free version of SPAMfighter for private users. It has removed 18156 spam emails to date. Paying users do not have this message in their emails. Try SPAMfighter for free now! |
#5
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Sony KV-35S26 - Picture collapses
And if the Black VDR was no good it would take out the 6.8ohm as well...not
to mention the 4834,s. You have missed a bad cap or still missed adry joint. kip "Leonard Caillouet" wrote in message ... Why would you replace the VDR in this case? The VDRs almost never go bad when the cause of the failure is the output stage shorting. Leonard "Dani" wrote in message ups.com... Replace VDR 601, it's black, there may be two depending on the model, they are by the two 2sc4834 regulators. They go bad sometimes. Be sure to resolder the horizontal drive, & check the electrolytic capacitor, if it has one, Dani. -------------------------------------------------------------------------------- I am using the free version of SPAMfighter for private users. It has removed 18156 spam emails to date. Paying users do not have this message in their emails. Try SPAMfighter for free now! |
#6
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Sony KV-35S26 - Picture collapses
Thanks for the help and suggestions. I'll recheck the soldering and
look for a bad cap. Juan |
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